Delayed Tumor Growth in Vestibular Schwannoma: An Argument for Lifelong Surveillance

Abstract

Objective: Previous research has shown that tumor growth during observation of small-to-medium sized sporadic vestibular schwannomas (VSs) occurs almost exclusively within 3 to 5 years following diagnosis. This has led some to consider ending surveillance after this interval. This study seeks to characterize a cohort of patients with tumors that exhibited late growth. Study Design: Retrospective cohort study. Setting: Tertiary referral center. Patients: Adults with sporadic VSs who initially elected observation with serial magnetic resonance imaging (MRI) surveillance. Intervention(s): None. Main Outcome Measure(s): Linear tumor growth was measured in accordance with AAO-HNS reporting guidelines. Delayed growth was defined as growth ≥2 mm in linear diameter that was first detected 5 years or more from the initial MRI. Results: From a total of 361 patients, 172 experienced tumor growth during the interval of observation. Fourteen of these 172 patients (8.1%) experienced late growth occurring at 5 years or beyond. Among patients with delayed growth, the fastest growth rate after extended quiescence was 1.33 mm/yr, and the longest delay before tumor growth detection was 11.1 years. Additional treatment was recommended for six (42.9%) of the patients with delayed growth. Of 68 tumors that remained in the IAC, 11 (16.2%) demonstrated delayed growth. Of 66 tumors that presented in the CPA, 2 (3.0%) demonstrated delayed growth. Initial size was larger for tumors demonstrating early growth compared with those with delayed growth. For tumors within the IAC, those with early growth had a significantly higher median growth rate than those with delayed growth (1.40 vs. 0.45 mm/yr, p < 0.001). Conclusions: Delayed growth encompassed 8.1% of growing VSs and 3.9% of all observed tumors. Patients with delayed growth exhibited slower growth rates compared with those who were diagnosed with growth early in their observation course. These findings support the need for lifelong surveillance of untreated VSs given the possibility of clinically significant delayed growth. Increasing the time interval between MRI studies after 5 years is a reasonable concession to balance practicalities of cost and convenience with risk of delayed of tumor growth.

Cochlear Implantation Outcomes in Observed Vestibular Schwannoma: A Preliminary Report

“…22 A smaller proportion (4%-8%) may exhibit delayed growth up to 11 years after diagnosis. 23 These findings highlight the importance of early and long-term surveillance of tumor size, which must be considered prior to CI.…”

“…In a recent study, Lees et al showed that a majority of VS tumors demonstrate early growth (68%) within the first years of diagnosis, defined as at least a 20% increase in size on volumetric analysis 22 . A smaller proportion (4%‐8%) may exhibit delayed growth up to 11 years after diagnosis 23 . These findings highlight the importance of early and long‐term surveillance of tumor size, which must be considered prior to CI.…”

“…22 A smaller proportion (4%-8%) may exhibit delayed growth up to 11 years after diagnosis. 23 These findings highlight the importance of early and long-term surveillance of tumor size, which must be considered prior to CI. Historically there have been challenges with surveillance imaging of VS in the setting of prior CI due to implant artifact.…”

Wait and Scan Management of Intra-canalicular Vestibular Schwannomas: Analysis of Growth and Hearing Outcome

“…On the contrary, we still recommend lifelong surveillance as 7.8% of our cases started to grow after 5 years. Prolonged surveillance has also been recommended by other investigators based on similar findings (10,11,21–24).…”

The biological underpinnings of radiation therapy for vestibular schwannomas: Review of the literature

“…Tumor control rate (stable or decreased size) is 91%, while approximately 9% of the tumors are radioresistant; some tumors continue to grow despite high doses of radiation 45 . All this suggests that unlike malignant tumors, VS are particularly radioresistant, so clinical surveillance is required indefinitely in irradiated VS 46 . This relative resistance to radiation is not surprising given the low proliferative capacity of VS cells reflected in the slow clinical growth rate of VSs.…”